Reeve wrote:Do physicists dare go near the apparent philosophical implications? I assume not (?)

What philosophical implications?

There are "wow" moments, where you see everything differently. Once I walked around in a daze for a day, when I perceived everything around me in terms of quantum entanglement and decoherence. But this happens so often when you study science.

There are, I think, various meaningful philosophical implications, but I have yet to find a philosopher who could be arsed. They mostly seem to go for superficial understandings and far too many assumptions.

epepke wrote:

Reeve wrote:Do physicists dare go near the apparent philosophical implications? I assume not (?)

What philosophical implications?

There are "wow" moments, where you see everything differently. Once I walked around in a daze for a day, when I perceived everything around me in terms of quantum entanglement and decoherence. But this happens so often when you study science.

There are, I think, various meaningful philosophical implications, but I have yet to find a philosopher who could be arsed. They mostly seem to go for superficial understandings and far too many assumptions.

The implication that the future is "out there" already in space-time and that the past still is.

Reeve wrote:The implication that the future is "out there" already in space-time and that the past still is.

That really doesn't make any difference. If it makes a difference for philosophy, then philosophy is even more superficial than I thought.

It doesn't matter if the future is out there already. What matters is how information goes. Maxwell's Equations work just as well back as forward in time. So why can't you hear the radio broadcast from tomorrow? Why doesn't a signal go back in time?

Feynman's answer was that it does go back in time, but it hits something, and that reflects a signal forward in time. The signals cancel out, and your radio can't detect it. It's too bad that he didn't live to know that the universe is always getting bigger, which would make that make sense, because in the past there's no place to miss, whereas in the future there are lots of places to miss. Of course, it could also be that the signals are being reflected by the beginning of the universe itself.

So even if the future is out there, it doesn't really matter, because you can't do anything about it.

If that doesn't make sense, it is what I mean when I say that philosophers aren't interested.

Various authors have, surprisingly, dealt with similar ideas that make sense. Philip K. Dick, for example, wrote about precogs, but usually had the idea that the nature of precognition is such that, if you have knowledge of the future, the universe is constructed in such a way that you cannot do anything to change it, no matter how hard you try. This makes a weird kind of quantum sense. In The World Jones Made, Jones describes the feeling of precognition as follows: While everybody else was amazed by his precognitions, his experience was that, when an event happened, he remembered it as having happened a year ago. That's interesting.

epepke wrote:

Reeve wrote:The implication that the future is "out there" already in space-time and that the past still is.

That really doesn't make any difference. If it makes a difference for philosophy, then philosophy is even more superficial than I thought.

You're right. The philosophical difference is that it implies fatalism i.e no free will.

epepke wrote:What philosophical implications?

@epepke

In terms of the philosphical implications, it might be better to ask if you agree with some of the comments made by prof. Greene in the documentary. For example:

Firstly, is the representation, here, of the experience of time, for relatively moving observers, an accurate reflection of what Einsteinian relativity says should occur?


If so, would you agree with the following?
[quote=prof.Greene]once we know that your now can be what I consider the past; or your now can be what I consider the future; and your now is every bit as valid as my now; then we learn that the past, must be real, the future, must be real; it could be your now; that means past, present, and future, all equally real[/quote]
[url="http://www.youtube.com/watch?v=ppWV4UM-_LY&feature=relmfu#t=25m26s"]prof.Greene statement[/url]

Do you agree that [what you consider to be] the past still exists and [what you consider to be] the future already exists; and that such is necessitated by Einsteinian relativity, or the relativity of simultaneity in particular?


Does it follow?
I'll also paraphrase what someone else said in a discussion on the same subject; firstly, would you agree that time dilation is a real effect, that time actually slows down for relatively moving observers; as opposed to the slower ticking clock simply being an optical illusion.

Would you agree that only the block universe concept allows for time dilation to be a real, as opposed to an optical, effect; that is, if time dilation is real, then it follows that what I consider to be the past could be yours, or someone elses, present, and the same with my future; from this follows the block universe concept?

mangaroosh wrote:

epepke wrote:What philosophical implications?

@[color=#CC0000][b]epepke[/b][/color]

In terms of the philosphical implications, it might be better to ask if you agree with some of the comments made by prof. Greene in the documentary. For example:

Firstly, is the representation, here, of the experience of time, for relatively moving observers, an accurate reflection of what Einsteinian relativity says should occur?

It's a pretty accurate representation of Special Relativity at a high-school level, yes.

If so, would you agree with the following?
[quote=prof.Greene]once we know that your now can be what I consider the past; or your now can be what I consider the future; and your now is every bit as valid as my now; then we learn that the past, must be real, the future, must be real; it could be your now; that means past, present, and future, all equally real

[url="http://www.youtube.com/watch?v=ppWV4UM-_LY&feature=relmfu#t=25m26s"]prof.Greene statement[/url]

Do you agree that [what you consider to be] the past still exists and [what you consider to be] the future already exists; and that such is necessitated by Einsteinian relativity, or the relativity of simultaneity in particular?[/quote]

I agree that it's real. I interpret "already exists" as being in the past with respect to the observer's light cone, so no, I don't agree that it already exists.

And if you are going to define "already exists" in some other way, what of it?

I'll also paraphrase what someone else said in a discussion on the same subject; firstly, would you agree that time dilation is a real effect, that time actually slows down for relatively moving observers; as opposed to the slower ticking clock simply being an optical illusion.

Yes, and the optical illusion is quite different. Objects appear almost to be rotated, by skewing, such that they are pointing away, and you see their butts.

Would you agree that only the block universe concept allows for time dilation to be a real, as opposed to an optical, effect; that is, if time dilation is real, then it follows that what I consider to be the past could be yours, or someone elses, present, and the same with my future;

Not for you and I, except over very small time scales, because we're too close. But sure, for sufficiently distant events.

from this follows the block universe concept?

I still don't know what the "block universe concept" is. It seems to me what Daniel Dennett, with a coinage of one of the daughters of one of his friends, called a "deepity." That's a statement that is trivially and uninterestingly true, and also interestingly false or nonsensical. I think he used the example "love is a word." Well, sure it is. So is "potato." But what of it?

As Nietzsche wrote, it gives the illusion of profundity, whereas it isn't even superficial.

epepke wrote:It's a pretty accurate representation of Special Relativity at a high-school level, yes.

Does Special Relativity materially change at university, or professional, level such that the representation is rendered false?

epepke wrote:I agree that it's real. I interpret "already exists" as being in the past with respect to the observer's light cone, so no, I don't agree that it already exists.

And if you are going to define "already exists" in some other way, what of it?

If we clarify what is meant by "already exists", or what is meant by the past and future being real, then we might be able to make some [additional, perhaps] deductions about the physical representation of the mathematics of relativity. That is, we might be able to bring meaning to them.

epepke wrote:Yes, and the optical illusion is quite different. Objects appear almost to be rotated, by skewing, such that they are pointing away, and you see their butts.

OK, so time dilation is a real phenomenon, as opposed to an optical illusion. That gives us another point on which we can build.

epepke wrote:

Would you agree that only the block universe concept allows for time dilation to be a real, as opposed to an optical, effect; that is, if time dilation is real, then it follows that what I consider to be the past could be yours, or someone elses, present, and the same with my future;

Not for you and I, except over very small time scales, because we're too close. But sure, for sufficiently distant events.

Apologies, whenever I refer to you and I in that sense, please take it to mean for observers moving relative to each other at a sufficient fraction of the speed of light, or for sufficiently distant events.

epepke wrote:I still don't know what the "block universe concept" is. It seems to me what Daniel Dennett, with a coinage of one of the daughters of one of his friends, called a "deepity." That's a statement that is trivially and uninterestingly true, and also interestingly false or nonsensical. I think he used the example "love is a word." Well, sure it is. So is "potato." But what of it?

As Nietzsche wrote, it gives the illusion of profundity, whereas it isn't even superficial.

It may well be a deepity, but it appears to be a deepity that is being propagated in the mainstream as being a necessary consequence of Einsteinian relativity. But we can perhaps ignore the title "block universe" and just focus on some of the points of agreement; see if there are other points of agreement; and see what are the necessary conclusions we can draw.


Equally real?
I am I right in taking your statement above, "I agree that it's real", to refer to the fact that you agree that [what you consider to be] the past is real, and [what you consider to be] the future is real; by this can we imply that you believe they exist in some sense; that they exist in the sense that your present moment (what you consider to be "now") exists? If not, then you must consider the present to either be more valid than the past or the future or, at least, there must be a difference in validity i.e. they are not equally real.

In short, would you say that [what you consider to be] the past, [what you consider to be] the present, and [what you consider to be] the future, are all equally real; that all equally exist?


Relativity of Simultaneity
Would you agree that, if time dilation is a real phenomenon, as opposed to an optical illusion, it implies that what one observer considers to be the past could represent what another observer considers to be the present; or what another observer considers to be the future; which, taken together means that "my past", "my present", and "my future" all co-exist, and are all equally real; with the same being true for you and everyone else in the universe?

mangaroosh wrote:...which, taken together means that "my past", "my present", and "my future" all co-exist, and are all equally real; with the same being true for you and everyone else in the universe?

No, because you cannot be in two places at once, or in two reference frames at once. Thus, the relativity of your simultaneity depends on an observer other than yourself. You cannot mix up your own past/present/future.

epepke wrote:Various authors have, surprisingly, dealt with similar ideas that make sense. Philip K. Dick, for example, wrote about precogs, but usually had the idea that the nature of precognition is such that, if you have knowledge of the future, the universe is constructed in such a way that you cannot do anything to change it, no matter how hard you try. This makes a weird kind of quantum sense. In The World Jones Made, Jones describes the feeling of precognition as follows: While everybody else was amazed by his precognitions, his experience was that, when an event happened, he remembered it as having happened a year ago. That's interesting.

I haven't read that one. But I would claim that you can't really remember something unless you were causally connected to it, even if what you remember really happened. It's like the Gettier problems. So I'd say the same thing about precognition in this case, which means that it can go by the much less glamorous name of "planning". Plans go wrong, because our future memories are often unreliable, but if you have a precognition that someone will die, it needs to be correctly identified for the conspiracy to commit murder which it is.

I think this thread could be retitled as "what awesome stories are made possible by thinking about a block universe?", because I think if philosophy is ever going to be useful, it needs to get more into the business of sci-fi and horror fiction. The philosophy of mind types have made more progress with this than anyone else, and literally spend half their time talking about the Matrix and ghosts and zombies, and what properties a real ghost should have and what properties a real zombie should have.

DavidMcC wrote:

mangaroosh wrote:...which, taken together means that "my past", "my present", and "my future" all co-exist, and are all equally real; with the same being true for you and everyone else in the universe?

No, because you cannot be in two places at once, or in two reference frames at once. Thus, the relativity of your simultaneity depends on an observer other than yourself. You cannot mix up your own past/present/future.

It isn't a case of mixing up ones own past present and future, its a case of whether what you consider to be the past continues to exist, and is as real as your present; and what you consider to be the future already exists and is as real as your present. What you consider the past could be part of the present for an observer moving relative to you, in a given direction and at a given velocity. In order for relativity of simultaneity to refer to real and physical events, as opposed to RoS of events which are an optical illusion, this would seem to be necessitated; or so some would claim, as per the documentary with prof. Greene.

Events
I could be considered an event just like anything else couldn't I? The co-ordinates of me, at a given time and place would be considered the co-ordinates of an event; if that event of me is simultaneous with two flashes of lightning say, in my reference frame, and we do a Lorentz transform on those co-ordinates, for a reference frame moving relative to "that event of me" at a sufficient fraction of the speed of light, we would find that that event of me at the given time and place wasn't simultaneous with the two lightning flashes, in that relatively moving reference frame. This would seem to have implications for the existence of "my past self" and "my present self".

You and me
Lets say you and me are at rest relative to each other; that means that the events that we refer to as "my present self" are simultaneous with each other. Then imagine that we start moving relative to each other at a sizable fraction of the speed of light; given time dilation, RoS, and length contraction, the events that we term "my present self" are no longer simultaneous with each other. This also appears to have implications for the idea of "my past self" and "my future self".

VazScep wrote:I think this thread could be retitled as "what awesome stories are made possible by thinking about a block universe?", because I think if philosophy is ever going to be useful, it needs to get more into the business of sci-fi and horror fiction. The philosophy of mind types have made more progress with this than anyone else, and literally spend half their time talking about the Matrix and ghosts and zombies, and what properties a real ghost should have and what properties a real zombie should have.

That could be the title of another thread. The intention of this one is to see if the idea being propagated in the mainstream, namely that the block universe is a logical necessity of Einsteinian relativity, is accurate.

All time travel stories rely on the block universe. So that's a huge bulk of pop. culture sci-fi right there!

mangaroosh wrote:

epepke wrote:It's a pretty accurate representation of Special Relativity at a high-school level, yes.

Does Special Relativity materially change at university, or professional, level such that the representation is rendered false?

No, but the language gets better and more precise, and you get a deeper understanding that makes it a lot easier to make the transition to General Relativity.

At some level of understanding, the idea "a blanket is warm" is pretty good. At another level, "a blanket insulates and prevents heat loss via conduction" is better.

If we clarify what is meant by "already exists", or what is meant by the past and future being real, then we might be able to make some [additional, perhaps] deductions about the physical representation of the mathematics of relativity. That is, we might be able to bring meaning to them.

That might be so. Would someone like to try? I don't see that it has been done. It's like the old saying, "If I had some pork, I could make some pork and beans, if I had any beans."

It seems to me that you're saying, "If I were saying something meaningful, then it might be meaningful, dammit!" I'm saying, "OK, go ahead."

It may well be a deepity, but it appears to be a deepity that is being propagated in the mainstream as being a necessary consequence of Einsteinian relativity. But we can perhaps ignore the title "block universe" and just focus on some of the points of agreement; see if there are other points of agreement; and see what are the necessary conclusions we can draw.

I think that "consequence" probably means something other than "redefinition."

I am I right in taking your statement above, "I agree that it's real", to refer to the fact that you agree that [what you consider to be] the past is real, and [what you consider to be] the future is real; by this can we imply that you believe they exist in some sense; that they exist in the sense that your present moment (what you consider to be "now") exists?

Yes.

In short, would you say that [what you consider to be] the past, [what you consider to be] the present, and [what you consider to be] the future, are all equally real; that all equally exist?

Yes.

Would you agree that, if time dilation is a real phenomenon, as opposed to an optical illusion, it implies that what one observer considers to be the past could represent what another observer considers to be the present; or what another observer considers to be the future; which, taken together means that "my past", "my present", and "my future" all co-exist,

Yes, with the following caveat. A lot of events are neither in the past nor in the future, and they certainly aren't in the present, either. These are events separated by spacelike intervals. With respect to an observer, the number of events in the universe for which the terms "past," "present," and "future" even have any meaning is pretty small. This is the kind of thing that is taught past high school, and I don't think this block universe stuff adequately conveys it, if it conveys it at all.

epepke wrote:No, but the language gets better and more precise, and you get a deeper understanding that makes it a lot easier to make the transition to General Relativity.

At some level of understanding, the idea "a blanket is warm" is pretty good. At another level, "a blanket insulates and prevents heat loss via conduction" is better.

Those two statements aren't necessarily the same though, as there is nothing inherently warm about a blanket; it might be better to say "a blanket can help keep you warm", or something to that effect. In that context the latter becomes more a statement of how the blanket works. While it might be useful, at certain levels to understand how a blanket keeps you warm, there are certain questions, even at higher levels where simply knowing that a blanket keeps you warm is sufficient.

For example, understanding that the reason one person's past could be another persons future, or present, etc. is due to Relativity of Simultaneity, isn't necessary to discuss some of the consequences of the idea that what you consider to be the past continues to exist, and is as real as what you consider to be the present.

epepke wrote:

If we clarify what is meant by "already exists", or what is meant by the past and future being real, then we might be able to make some [additional, perhaps] deductions about the physical representation of the mathematics of relativity. That is, we might be able to bring meaning to them.

That might be so. Would someone like to try? I don't see that it has been done. It's like the old saying, "If I had some pork, I could make some pork and beans, if I had any beans."

It seems to me that you're saying, "If I were saying something meaningful, then it might be meaningful, dammit!" I'm saying, "OK, go ahead."

I was simply addressing your question, "what of it?". What of it is that we might be able to draw some inferences about what is necessitated by such a position; it wouldn't be worth outlining some of those potential inferences, without first seeing what the points of agreement are, and seeing what they mean.

The concept of Relativity of Simultaneity, for example, is an empty concept until we discuss it and bring meaning to it; the idea that an event which has specific time co-ordinates in one reference frame, might have different co-ordinates in another relatively moving reference frame is meaningless until we understand the relevance of an objects time co-ordinates.

epepke wrote:I think that "consequence" probably means something other than "redefinition."

Another point of agreement; the question in the given context, however, might be whether you believe the consequences painted by prof.Greene, in the documentary, are necessary consequences of Einsteinian relativity, or if they represent a redefinition of the theory?

epepke wrote:

I am I right in taking your statement above, "I agree that it's real", to refer to the fact that you agree that [what you consider to be] the past is real, and [what you consider to be] the future is real; by this can we imply that you believe they exist in some sense; that they exist in the sense that your present moment (what you consider to be "now") exists?

Yes.

In short, would you say that [what you consider to be] the past, [what you consider to be] the present, and [what you consider to be] the future, are all equally real; that all equally exist?

Yes.

OK, can we assume that for your past, present, and future all to exist, that they must be extended temporally, or "through time"; akin to, but not the same as, how a line is extended through space; two points on the line don't occupy the same space, and two moments don't occupy the same time?

Can we also assume that you believe that what you consider to be the past, the present, and the future must all be physically connected; that is, there is no empty space or time between them?

epepke wrote:Yes, with the following caveat. A lot of events are neither in the past nor in the future, and they certainly aren't in the present, either. These are events separated by spacelike intervals. With respect to an observer, the number of events in the universe for which the terms "past," "present," and "future" even have any meaning is pretty small. This is the kind of thing that is taught past high school, and I don't think this block universe stuff adequately conveys it, if it conveys it at all.

This is a point I haven't encountered before; surely all events must fall into one of the three categories:
- what you, or I, consider to be the past
- what you, or I, consider to be the present
- what you, or I, consider to be the future

When you say events separated by spacelike intervals, do you simply mean something like an event in the USA and an event in London?

mangaroosh wrote:I could be considered an event just like anything else couldn't I? The co-ordinates of me, at a given time and place would be considered the co-ordinates of an event; if that event of me is simultaneous with two flashes of lightning say, in my reference frame, and we do a Lorentz transform on those co-ordinates, for a reference frame moving relative to "that event of me" at a sufficient fraction of the speed of light, we would find that that event of me at the given time and place wasn't simultaneous with the two lightning flashes, in that relatively moving reference frame. This would seem to have implications for the existence of "my past self" and "my present self".

Your past and present selves may be influenced by your perception of the two lightning flashes, it's true. Therefore a remote observer, in a different reference frame could possibly find your reactions to the two flashes rather strange, if they seem to occur in the reverse order from the way you actually experienced them. (For example, you might have shielded your eyes from flashes after what was the first flash for you, but you would seem to be unshielding your eyes before the second flash to the observer!) In other words, he would see your time apparently going in reverse, although you would not!

mangaroosh wrote:

epepke wrote:Yes, with the following caveat. A lot of events are neither in the past nor in the future, and they certainly aren't in the present, either. These are events separated by spacelike intervals. With respect to an observer, the number of events in the universe for which the terms "past," "present," and "future" even have any meaning is pretty small. This is the kind of thing that is taught past high school, and I don't think this block universe stuff adequately conveys it, if it conveys it at all.

This is a point I haven't encountered before; surely all events must fall into one of the three categories:
- what you, or I, consider to be the past
- what you, or I, consider to be the present
- what you, or I, consider to be the future

When you say events separated by spacelike intervals, do you simply mean something like an event in the USA and an event in London?

Suppose you have lunch at 12pm today. Suppose, also that Zog also has lunch at a particular time/day on a planet in Andromeda. Unless you can send a light (or slower) signal between your lunch event and Zog's lunch event, it's meaningless to say whether his lunch event is in the future or past of your lunch event. If you can't connect the events with such a signal, the two events are said to be spacelike separated.

Now, you *could* in principle strew the space between here and Andromeda with clocks, place one every meter say, and synchronize them with your home clock using light pulses. Then when Zog has his lunch, he could stop the clock nearest to him. You could then go there and collect it and compare the recorded time with the time you had lunch. You could then say if his lunch was to the future of your lunch.

But you've only achieved this designation *with respect to the coordinate system (the clocks) you've set up". It has no fundamental "invariant" meaning. It is purely artificial. Someone else zapping around in a rocket might record different times and ordering for the two events.

deleted - double post

twistor59 wrote:Suppose you have lunch at 12pm today. Suppose, also that Zog also has lunch at a particular time/day on a planet in Andromeda. Unless you can send a light (or slower) signal between your lunch event and Zog's lunch event, it's meaningless to say whether his lunch event is in the future or past of your lunch event. If you can't connect the events with such a signal, the two events are said to be spacelike separated.

Now, you *could* in principle strew the space between here and Andromeda with clocks, place one every meter say, and synchronize them with your home clock using light pulses. Then when Zog has his lunch, he could stop the clock nearest to him. You could then go there and collect it and compare the recorded time with the time you had lunch. You could then say if his lunch was to the future of your lunch.

But you've only achieved this designation *with respect to the coordinate system (the clocks) you've set up". It has no fundamental "invariant" meaning. It is purely artificial. Someone else zapping around in a rocket might record different times and ordering for the two events.

Cheers twistor, I am familiar with the idea you're talking about and have heard the term "spacelike separation" before, but didn't know it referred to that phenomenon.

Some of that seems somewhat strange to me, for the simple fact that we cannot send an instantaeous light signal to any location that is any distance apart from us, so theoretically we could never say that anything is in our present. The idea of sending a light signal between our lunch times obscures the issue a little bit, because we imagine lunchtime to be of a certain duration; but, if we consider events of sufficiently short duration, such that by the time we send a light pulse from where we are, to where it is, that event would have finished, we could conclude that we can never say anything is in our present, despite knowing that somethings must be.

If we take an event which occurs just one metre away from us, and imagine that event to be of sufficiently short duration, that by the time we send the light pulse to it, it would have finished; while the event might have actually been in our present, it would fail the test above.

Zog
I'll try and say it somewhat clearer in terms of Zog, because even the above isn't that clear to me

Let's not take a specific event for Zog or ourselves; let's take "now", an idea we are all familiar with, even if it doesn't lend itself to easily to definition. Assuming the existence of the universe other than where we are, Andromeda for example, then we can reasonably deduce that right now, in other parts of the universe, something must be happening, regardless of what it is. In Andromeda Zog could be just getting up, he could be having his lunch, or he might not even be conceived yet; either way, we can reasonably imagine that right now, other locations in the universe exist and things, or events, are happening, even if we cannot determine, precisely, what those things, or events are. Those events would make up what we consider to be the present. We can also reasonably deduce that events occurred before those events, and will occur after those events; even if we cannot determine what they are, those events would still be categorised as what we consider to be the past, present, and future.


Relativity of Simultaneity
Now, taking into account RoS, and as you mention; a relatively moving observer might record the times and ordering of those events differently; that such an observer could make such an observation has physical implications for the structure of the universe; assuming that those events are real, physical and not simply optical illusions. Such a conclusion implies something about the structure of the universe, and events, something which might be deducible. Block universe theorists seem to believe that the implications of RoS imply a block like structure extended through time.

But leaving the block universe aside, can we deduce what it means for us in particular? Some people seem to believe that RoS implies that events which we consider to be the present, as outlined above, could be what another observer considers the future; and events that another observer considers to be the present, could be what we consider to be our past, or indeed, our future.

Would you say that that is a fair deduction, on their behalf?

DavidMcC wrote:Your past and present selves may be influenced by your perception of the two lightning flashes, it's true. Therefore a remote observer, in a different reference frame could possibly find your reactions to the two flashes rather strange, if they seem to occur in the reverse order from the way you actually experienced them. (For example, you might have shielded your eyes from flashes after what was the first flash for you, but you would seem to be unshielding your eyes before the second flash to the observer!) In other words, he would see your time apparently going in reverse, although you would not!

From that example though, can we deduce that relativity of simultaneity implies that what I consider to be my "past self", let's say "me of 20mins ago", must co-exist - although temporally separated - with what I consider to be "my present self"; that is, that "my past self" continues to exist?

mangaroosh wrote:

DavidMcC wrote:Your past and present selves may be influenced by your perception of the two lightning flashes, it's true. Therefore a remote observer, in a different reference frame could possibly find your reactions to the two flashes rather strange, if they seem to occur in the reverse order from the way you actually experienced them. (For example, you might have shielded your eyes from flashes after what was the first flash for you, but you would seem to be unshielding your eyes before the second flash to the observer!) In other words, he would see your time apparently going in reverse, although you would not!

From that example though, can we deduce that relativity of simultaneity implies that what I consider to be my "past self", let's say "me of 20mins ago", must co-exist - although temporally separated - with what I consider to be "my present self"; that is, that "my past self" continues to exist?

Not to you, though. Perhaps to the remote observer in a different inertial frame.